The use of communications networks, e.g., telephone systems, is becoming increasingly important as many businesses and individuals rely on these communications networks for both business and personal matters. With the increased use of communications networks it is also becoming increasingly important that such communication systems be provided in a reliable and cost effective manner.
At the present time, telephone companies and network providers are continuing to upgrade services by, e.g., installing fiber optic lines between central offices and more recently, between end offices and subscriber loop carrier systems. A subscriber loop carrier system allows the central office telephone line interface to be extended great distances from the central office using a high speed digital pathway, typically a fiber optic link. Optical network units (ONU) are used to couple the fiber optic lines in said subscriber loop carrier systems to conventional twisted copper telephone lines which, in most cases, complete the link to the end user of the communication service. Such conventional telephone lines are frequently referred to as drop pairs because they comprise a pair of wires dropping to the customer at the last portion of the telephone system link. Because of the cost and complexity of fiber optic communications equipment, it is likely that copper wire, e.g., twisted pair, will continue to be the primary choice for providing service to end users at the last portion of the telephone system loop for many years to come. Such systems are sometimes referred to in the communication industry as plain old telephone service (POTS). It is also important to note that POTS service will continue to be delivered to the subscriber over copper pairs directly from the central office as well as from subscriber loop carrier systems without the use of fiber optics.
Unfortunately, the use of copper wire as a communication pathway has several disadvantages. First, copper lines are subject to interference and other fault conditions, such as opens and shorts, which can interrupt communications. Second, such transmission lines have limited bandwidth capacity and are usually only capable of serving as a single communication channel. Accordingly, in order to resolve fault conditions or add additional channel capacity or capabilities to an end user in such a system, it is generally necessary to replace an existing faulty line or add an additional line.
Such service is normally performed by sending a technician to the user's facilities to add a new line or replace an existing line. Such field service calls are costly because they occur at unpredictable times and require a technician to spend valuable time traveling to a user's facilities.
Accordingly, there is a need for methods and apparatus that will reduce service technician travel time, permit the scheduling of service in a predictable manner to make more efficient use of available service resources and to reduce peak service demands. At the same time the telephone service providers are trying to provide improved customer service response time in an increasingly competitive marketplace. To achieve such goals, it is desirable that a telephone company or other service provider be capable of substituting a functional line for a faulty one and/or adding an additional line to provide increased service to a user without having to send a technician to the user's residence or facilities.
While various digital communications systems such as those described in U.S. Pat. Nos. 5,365,510, 4,009,469 and 3,886,318 describe the use of an auxiliary communication pathway in the digital systems described therein, such systems are not well suited for use with POTS systems, frequently used as the communications channels to end users of telephone service, for several reasons.
First, such known digital systems are not designed to be powered from the limited current available from a POTS line. Second, the commands used to control switching in the known systems are digital signals which are relatively short complex signals which may be susceptible to interference present on POTS lines and furthermore, such digital signaling is typically not supported over common analog telephone circuits. In addition, because of the circuit complexity associated with the generation, detection, and decoding of the relatively short digital command signals used in the known systems, the known systems are more complex than is desirable for the implementation of an inexpensive telephone smart network interface device ("SNID").
Accordingly, there is a need for a method and apparatus that can be used to remotely provide a substitute communication line for a faulty line and/or can be used to provide an additional communication line to a user.
It is also highly desirable that such a SNID be capable of being powered from a standard POTS line, thereby avoiding the need for a separate power source and that it be simple and inexpensive to build.
In addition to the above features, the SNID should be responsive to command signals which can be readily generated by existing telephone tone signal generating equipment. Furthermore, the command signals used should be of a type which are not easily interfered with by power surges or other noise commonly found on POTS telephone lines.
Following the expectations of quality service in the communications systems as they exist today, the SNID should be transparent to various telephone system architectures, operations and various types of telephone termination equipment. It should have minimal impact on system reliability.
For cost reasons, it is also desirable that such switching apparatus be simple to implement and easy to install.